As a method of recording a face image and characters to a recording medium such as a bankbook and a card for personal identification in a financial institution such as a bank, there is a melting type thermal transfer recording method. In the case of recording characters to a recording medium using a melting type thermal transfer recording method, recording of a two-gradation image (binary image) may be performed. But in the case of recording a face image to a recording medium, since recording is performed using an area gradation method which changes a size of a dot to be transferred to the recording medium, it becomes necessary to practice various measures.
For example, there is an art which selects an optimum print parameter (an example of a control condition), based on an environmental temperature (ambient temperature) of a thermal head to be used in a melting type thermal transfer recording method, and a head temperature of the relevant thermal head, and controls the thermal head in accordance with the selected print parameter, to perform recording to a recording medium with a stable print density.
By the way, in a conventional art, print parameters for respective head temperatures are stored, in the case in which environmental temperatures of a thermal head and head temperatures of the thermal head are respectively same, and the thermal head is controlled using a print parameter corresponding to a detected head temperature of the thermal head, and thereby printing is performed with a stable print density. For the reason, when the difference between an environmental temperature and a head temperature of the thermal head becomes large, the difference between a detected head temperature of the thermal head and an effective head temperature becomes also large, and thereby it is not possible to perform printing with a stable print density.
Therefore, a method is also considered in which print parameters of all combinations of environmental temperatures of a thermal head and head temperatures of the thermal head are stored, and which controls the thermal head using a print parameter corresponding to the combination of an environmental temperature of the thermal head and a head temperature which have been detected, to perform printing with a stable print density. However, in order to store print parameters for the environmental temperatures from 0° C. to 63° C. in increments of 1° C., for respective head temperatures, it is necessary to provide a memory which can store print parameters that are 64 times as large as the present print parameters on a board.